Diabetes is an epidemic disorder that afflicts over 18 million people in the United States and is the fifth leading cause of death. Type 2 diabetes is the most common form and is characterized by systemic insulin resistance that cannot be corrected by increased insulin secretion. Activation of insulin receptor substrate (IRS) proteins by the insulin receptor is a critical step in the insulin signaling pathway. IRS proteins are recruited to the insulin receptor through PH and PTB domains located in the N-terminus. A unique domain in IRS2 termed the kinase regulatory loop binding (KRLB) region has been identified that interacts the tyrosine kinase domain of the insulin receptor. This region is potentially a key element that differentiates IRS2 function from that of IRS1. This study focuses on investigating the role of the KRLB region in regulating IRS2 function. Using site directed mutagenesis, mutations in the KRLB region will be generated and will be examined for their impact on IRS2 activity and insulin signaling in vitro and in vivo. In addition we will analyze how IRS2 function impacts IRS1 signaling using the KRLB mutants. These experiments will establish if the KRLB region of IRS2 impacts the cross talk between IRS1 and IRS2 signaling in the liver. PUBLIC HEALTH RELEVANCE: Diabetes and its subsequent complications are affecting an increasing number of people worldwide, therefore understanding the insulin signaling system and how insulin resistance develops is paramount. This research project aims to investigate how the unique KRLB region in IRS2 regulates IRS2 function and whether this region contributes to differences in IRS2 and IRS1 signaling. This information could reveal strategies to reverse the negative consequences of impaired insulin signaling and insulin resistance. [unreadable] [unreadable] [unreadable]